1. Field of the Invention
The invention concerns a method of determining the instantaneous angular position of a headlight, in particular for a motor vehicle, that is mounted so as to pivot about a rotation axis in a predetermined range of movement.
2. Description of the Related Art
Some motor vehicles are in fact equipped with front headlights that are mounted so as to rotate about a vertical axis. Such a headlight makes it possible, for example when a vehicle is approaching a bend, to illuminate the portion of roadway that is situated in the curvature of the bend.
The invention is also applicable to headlights that are mounted so as to rotate about a transverse axis so as to correct the elevation of the headlight according to irregularities in the road.
Existing headlights often comprise stepping actuators or stepping motors. Whenever the actuator is powered up, an initialization phase, prior to the use of the actuator, is necessary in order to calibrate it. During this initialization phase, the headlight is brought into a neutral angular position. This neutral angular position corresponds to an orientation of the headlight when the motor vehicle is traveling in a straight line and/or at a constant speed.
The actuator generally has end-of-travel stops. During normal initialization phases, the actuator is brought against the stops. The actuator is thus deployed over its entire travel, as far as one of the stops. This stop position is then taken as the reference angular position in order to return the headlight to its neutral angular position, for example by counting a predetermined number of steps. The reference angular position therefore corresponds to one of the extreme angular positions of the headlight.
However, traveling over the whole of the travel of the stepping actuator in order to obtain the reference angular position of the headlight causes an unwanted movement of the headlight. This unwanted movement of the headlight may cause a nuisance or dazzling for a motorist traveling in the opposite direction. This is because a motorist passing a vehicle whose headlight is in the initialization phase may be dazzled by this headlight since the reference angular position corresponds to an extreme angular position that is liable to illuminate the road on which the other motorist is traveling.
Moreover, the unwanted movement of the headlight routinely impairs the availability of the headlight. This is because traveling over the whole of the travel of the actuator requires a not insignificant length of time, for example three seconds.
Measurement devices are also known that comprise sensors called copying or recopying sensors. These sensors emit an electrical measurement signal whose value represents the position of the headlight over an intermediate range of the range of movement of the headlight.
Thus, over this intermediate range, a value of the signal emitted by the sensors is associated with each angular position of the headlight about its rotation axis. It is thus possible to determine, for each value produced, the exact instantaneous angular position of the headlight over the intermediate range of angular positions.
This type of measurement device comprises for example a fixed Hall effect sensor that measures the intensity of the magnetic field emitted by a magnet that is mounted so as to pivot integrally with the headlight.
However, such a copying sensor is very expensive and complex to manufacture and calibrate.
In addition, the sensitivity of this type of sensor is not sufficient to precisely determine the instantaneous angular position of the headlight in end ranges of the range of movement of the headlight.
In addition, when this type of measurement device comprises a Hall effect sensor, the measurements made by the sensor are liable to be influenced by external constraints such as temperature or vibrations.
What is needed, therefore, is a system and method that overcomes one or more of the problems in the prior art.